1. Field of the Invention
This invention generally relates to digital image processing and, more particularly, to a system and method for fingerprinting a print job.
2. Description of the Related Art
The origin and certain other details associated with the rendered output of a print job, are not conventionally embedded in the print job. Further, even the job characteristics that accompany a print job cannot be extracted, once the print job is printed. Thus, information concerning the origin of the print job, such as the desired anti-copy protection criteria, or the printer identification that produced the output, is lost. If this information is not printed with the document, administrators cannot detect or trace back the misuse of the printing devices, where confidentiality is an issue, or provide forensics information as to the source of a printout, when the document is associated with a crime investigation. The process of providing information about a document, with the document, when the document is rendered into an output, is referred to herein as fingerprinting.
FIG. 1A is a diagram illustrating a barcode fingerprint (prior art). One conventional fingerprinting means is barcoding. In this case, a barcode containing the fingerprint information is added to a part of the printed document in such a way as to not obscure the print image. For example, the barcode may be added to a binding edge, in a portion of the document that is not used for stapling or hole punching. Alternately, the barcode may be added to an unused area of a page footer. The barcode can subsequently be scanned to read the fingerprint information. Barcodes may contain a substantial amount of redundant information, so that they remain reliable, even after copying or rescanning.
FIG. 1B is a diagram depicting a serialized fingerprint (prior art). Another method of fingerprinting is serialization. In this case, a human readable text string containing the fingerprint information is added to a part of the printed output that does not contain the print image; as described for the barcode above. Generally, the text string contains an identifier for each printout that is used to uniquely identify each instance, for example, the serial number of a copy. The serial number can subsequently be read by a human, or scanned/OCR (optical character recognition), to recover the fingerprint information. The serial number fingerprints can be accurately copied with a high reliability.
FIG. 1C is a diagram depicting a watermark fingerprint process (prior art). Another method of fingerprinting is the use of a digital mark added to the printed output. For example, a digital mark may be added as a watermark. This method suffers in that it modifies the print image. If the digital mark is added “beneath” the print image (underlay), portions of the digital mark may be obscured by the print image, resulting in a loss of fingerprint information. If the digital mark is added above the print image (overlay), portions of the print image may be obscured by the digital mark, resulting in a lost of some of the print image. If overlapping parts of the print image and digital mark are merged together (composite), then a trade-off can be performed between the loss of fingerprint information vs. loss of print image. The digital mark can subsequently be recognized by either a human or scan process. Copying of the printed output may result in a deterioration of the fingerprint information.
Other methods of watermarking may include hiding a digital signature in the printed image. In pending patent application Ser. No. 10/617,483, entitled SECURITY FONT SYSTEM AND METHOD FOR GENERATING TRACEABLE PAGES IN AN ELECTRONIC DOCUMENT, invented by Mary Bourret, fingerprint information is embedded by altering the characteristics of a font set.
It would be advantageous if fingerprint information could be added to a print job seamlessly by an element of the spooling or despooling subsystem.
It would be advantageous if the spooling/despooling subsystem adding the fingerprint could be embedded in either a client computer device, print provider, or a print server, in the path between the print generator, such as a print driver, and the printer.